Just curious how things turned out?
If no progress try this.
1.Disconnect the "negative" cable
to the battery for testing purposes.
2.Disconnect the "S" and "R" terminal wires
going to the solenoid.
3.The "positive" battery cable must always remain connected to the solenoid.
We can verify several things with this setup,
and it will also prevent your starter from engaging while troubleshooting
due to the ground cable being disconnected.
Everything you test with your voltmeter will be connected in this way above.
1. the black ground voltmeter lead must "always"
be connected to the negative battery post. (A light clamp on item may be needed).
2. After making the above mentioned changes, first connect the voltmeter to see if you have 12volts on the downstream side(to the starter) from the solenoid.
2a. If yes? stop there replace your solenoid. There still could be other problems. But the solenoid needs replaced first.
No voltage? then proceed to step 3.
3. Connect the voltmeter to the "S" terminal wire which is disconnected from the solenoid. If voltage is present with ignition off or disconnected? Then you have found a problem. Also check your "R" terminal wire as well. Then get back us with your test results. I have my suspicions but don't want to get ahead of what needs to happen first.